CRM-14007 Viewsd6 - move definition into same file as d7

This looks like a crazy big commit but I have simply moved the table definition from one file to another to match the d7 structure so that I can bring back the D7 changes into d6 as I was getting crazily confused with them in 2 different files & felt that was causing greater risk of error.

The alterations below are false - e.g

-      'handler' => 'views_handler_sort',

+      'handler' => 'civicrm_handler_sort_date',

- these are 2 completely separate lines of code & looking at the individual commits makes that clear

The only change other than movement here is the switch to using the alter hook in line with d7. I will do a separate PR with the backported changes from d7